BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
[0001] The present invention relates to a digital information recording-reproducing apparatus,
or more in particular to a digital information recording-reproducing apparatus having
a time-base restoration function.
DESCRIPTION OF THE RELATED ART
[0002] The Institute of Television Engineers of Japan Journal Vol. 47, No. 4, April 1993,
pp. 494-499, describes a system conceived to transmit audio or video software through
radio wave or a cable to be recorded in each home.
[0003] In this conventional system, however, the rate at which software information is transmitted,
recorded and reproduced is fixed. Especially, no measure is taken to shorten the recording
time.
[0004] Also, the problem of the above-mentioned conventional system is that the sale or
rent which may be made of audio or video software requires management of information
on customers, number of days rented, etc.
[0005] One such system may be interactive, in which the user requests the video software
he wants from the transmitting end, and the software supplier transmits the desired
software. In such a case, however, it takes a predetermined length of time before
the wanted digital information signal is actually transmitted from the time the particular
video software is requested. More specifically, the transmitting end is required to
prepare the video data to be transmitted or to stand by until a transmission channel
becomes available. This leads to the problem that the user cannot determine the time
to start his VTR.
SUMMARY OF THE INVENTION
[0006] A first object of the invention is to obviate the above-mentioned problems and to
provide a digital information recording-reproducing apparatus having the functions
of shortening the recording time and restoring the signal on time base.
[0007] A second object of the invention is to obviate the above-mentioned problems and to
provide a digital information recording-reproducing apparatus capable of easily managing
information on customers, number of days rented, etc.
[0008] A third object of the invention is to obviate the above-mentioned problems and to
provide a digital information recording-reproducing apparatus simple to operate, in
which recording errors can be minimized.
[0009] In order to achieve the first object, according to the invention, there is provided
a digital information recording-reproducing apparatus in which software information
is transmitted by being reduced to 1/n temporally, the received software reduced to
1/n temporally is recorded in magnetic tape at a predetermined rate, and the recorded
signal is reproduced at the rate 1/n the recording rate.
[0010] In order to achieve the second object, according to the invention, there is provided
a digital information recording-reproducing apparatus in which control codes such
as the user number and the recording date are additionally recorded in the recording
signal so that the information on customers, number of days rented, etc. are managed
based on the added information at the time of reproduction.
[0011] According to a first method for achieving the third object of the invention, there
is provided a digital information recording-reproducing apparatus comprising a control
signal generator at the transmitting end for controlling the operating conditions
of recording-reproducing means (VTR), wherein an output signal of the control signal
generator is transmitted together with a digital information signal through transmission
means before recording, and a control signal detector at the receiving end is connected
with the receiver and produces an output signal thereby to control the VTR in recording
mode.
[0012] According to a second method for achieving the third object of the invention, there
is provided a digital information recording-reproducing apparatus comprising a control
signal generator at the transmitting end for controlling the operating conditions
of the VTR, second transmission means for transmitting an output signal of the control
signal generator, and a control signal detector at the receiving end, wherein an output
signal of the control signal generator is transmitted through the second transmission
means before starting the recording, the VTR is controlled in recording mode by the
output signal of the control signal detector, and the digital information signal transmitted
through the first transmission means is recorded by the VTR.
[0013] According to a third method for achieving the third object of the invention, there
is provided a digital information recording-reproducing apparatus wherein the magnetic
tape is divided into a number
a of recording areas (
a: integer of 1 or more) each assigned to one video software.
[0014] The recording time can be shortened to 1/n by recording the software information
temporally compressed to 1/n.
[0015] At the time of reproduction, the signal is reproduced at the rate 1/n the recording
rate, and therefore the time axis is expanded by n times to reproduce the original
software information before temporal compression.
[0016] At the time of reproduction, the control information including the user number and
recording date are read. In the case where the user number is different, however,
no reproducing operation is performed. In the case of software rental, on the other
hand, no reproducing operation is performed after the lapse of a predetermined time
from the recording. By so doing, information on customers, the number of days rented,
etc. can be managed appropriately.
[0017] According to the first method, the control signal for controlling the VTR in recording
mode is transmitted through the same transmission channel of radio wave or cable before
the digital information signal of the video software to be transmitted. A demodulator
at the receiving end, once it has received the control signal, immediately sets the
VTR in recording mode.
[0018] According to the second method, the control signal for controlling the VTR in recording
mode is transmitted through a second transmission channel such as the telephone line
different from the transmission channel for transmitting the digital information signal
before the digital information signal of the video software to be transmitted. A second
demodulator at the receiving end, once it has received this control signal, immediately
or after the lapse of a predetermined time, sets the VTR in recording mode.
[0019] According to the third method, the magnetic tape is divided beforehand (preformatted)
into a plurality of recording areas, each of which is assigned to a video software
for sequentially recording the video data from the tape starting section. In the process,
the recording information on the video data that has been recorded in each area is
recorded in the header or tail section of the particular area, and according to the
contents of the recording information, the next area to be recorded is automatically
selected.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020]
Fig. 1 is a block diagram showing a digital information recording-reproducing apparatus
according to an embodiment of the invention.
Fig. 2 is a block diagram showing an example configuration of a recording encoder
according to the invention.
Fig. 3 is a diagram showing input and output signals of the recording encoder shown
in Fig. 2.
Fig. 4 is a diagram showing an example configuration of an ID signal.
Fig. 5 is a diagram showing a recording track pattern according to the embodiment
shown in Fig. 1.
Fig. 6 is a diagram showing a reproducing track pattern according to the embodiment
shown in Fig. 1.
Fig. 7 shows waveforms representing the reproducing operation according to the embodiment
shown in Fig. 1.
Fig. 8 is a block diagram showing an example configuration of a reproducing decoder
according to the invention.
Fig. 9 is a block diagram showing a digital information recording-reproducing apparatus
according to another embodiment of the invention.
Fig. 10 is a block diagram showing an example configuration of a recording encoder
according to the invention.
Fig. 11 is a diagram showing an example configuration of a control signal.
Fig. 12 is a diagram showing a control signal recording system according to another
embodiment.
Fig. 13 is a diagram showing a reproducing track pattern according to still another
embodiment of the invention.
Fig. 14 shows waveforms representing the reproducing operation according to a further
embodiment of the invention.
Fig. 15 is a block diagram showing an example configuration of a reproducing decoder
according to the invention.
Fig. 16 is a diagram showing an example configuration of the control signal according
to the embodiment shown in Fig. 9.
Fig. 17 is a block diagram showing a digital information recording-reproducing apparatus
according to still another embodiment of the invention.
Fig. 18 is a diagram showing an example configuration of the output signal of a transmitting
encoder according to the invention.
Fig. 19 is a block diagram showing a digital information recording-reproducing apparatus
according to still another embodiment of the invention.
Fig. 20 is a diagram showing divisions of the magnetic tape into areas according to
another embodiment.
Fig. 21 is a diagram showing an arrangement of recording information signals according
to a further embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] Embodiments of the present invention will be described below with reference to the
accompanying drawings.
[0022] A block diagram of a digital information recording-reproducing apparatus according
to an embodiment of the invention is shown in Fig. 1. This apparatus roughly comprises
a transmission system 100, a receiving system 200, and a recording-reproducing system
300. Numeral 1 designates an input terminal, numeral 10 a transmitting encoder, numeral
20 a time-base reduction circuit, numeral 25 a modulator, numeral 30 a transmission
channel, numeral 35 a demodulator, numeral 40 a recording encoder, numeral 45 a change-over
switch, numeral 50 a rotary drum, numerals 51a, 51b magnetic heads, numeral 60 a magnetic
tape, numeral 70 a reproducing decoder, numeral 80 a receiving decoder, and numeral
9 an output terminal. In the magnetic heads 51a 51b, (+) designates a positive azimuth,
and (-) a negative azimuth.
[0023] In the transmission system 100 shown in Fig. 1, the digital information signal inputted
from the input terminal 1 is encoded in a predetermined format by the transmitting
encoder 10. The signal thus encoded is reduced temporally to 1/n by the time-base
reduction circuit 20 to increase the transmission rate by n times, followed by modulation
at the modulator 25. The signal thus modulated is sent out on the transmission channel
30.
[0024] In the receiving system 200, the signal received through the transmission channel
30 is demodulated at the demodulator 35. The signal thus demodulated is applied as
it is to the recording encoder 40 of the recording-reproducing system 300 directly.
The signal thus applied is encoded by the recording encoder 40 in a format suitable
for recording and reproduction.
[0025] A block diagram representing an example configuration of the recording encoder 40
is shown in Fig. 2. Numeral 41 designates a memory, numeral 42 an interface circuit,
numeral 43 a parity generator, and numeral 44 a recording signal generator. In Fig.
2, the data demodulated at the demodulator 35 of the receiving system 200 is stored
first in the memory 41 through the interface circuit 42. The demodulated data is shown
in Fig. 3(A). The parity generator 42 generates a parity from the demodulated data
stored in the memory 41, and the parity thus generated is stored in the memory 41.
The recording signal generator 43 reads the parity and the demodulated data from the
memory 41, and adding a sync signal and an ID signal, produces a signal in block form
as shown in Fig. 3(B). Fig. 4 shows an example configuration of the ID signal constructed
of, for example, a track number for identifying the recording track, a block number
for identifying the in-track position, a control code such as the program number or
the recording time on tape and a parity for detecting and correcting an error of the
ID signal.
[0026] The signal thus encoded for the recording system is applied to the magnetic heads
51a, 51b mounted at 180 degrees to each other on the rotary drum 50 and is recorded
in azimuth on the magnetic tape 60. Assume that the rotation speed of the rotary drum
50 is R
1 and the traveling speed of the magnetic tape 60 is V
1. This recording track pattern is shown in Fig. 5. Character P designates a track
pitch, and character W the width of the magnetic heads 51a, 51b. According to the
embodiment under consideration, the head width W is set larger than the track pitch
P at, say, 1.5 times as large as the track pitch P.
[0027] At the time of reproduction, the rotary drum 50 is rotated at a speed of
, that is, m/n times (
) the rotational speed for recording, the magnetic tape 60 is run at a speed of V
1/n that is 1/n times the speed for recording, and the signal thus recorded is reproduced
by the magnetic heads 51, 51b.
[0028] Fig. 6 is a diagram showing the reproducing track pattern, in which the solid line
represents a recorded track pattern and the dashed line a scanning trace of the magnetic
heads 51a, 51b. In this way, the rotary drum 50 is rotated at a speed of
that is m/n times the rate for recording and the magnetic tape 60 is run at a speed
of V
1/n that is 1/n times the rate for recording. Therefore, the scanning pitch of the
magnetic heads 51a, 51b is 1/m times the track pitch P. In spite of a small deviation
of the scanning angle, therefore, substantially a number m of scans are effected per
track. According to the present embodiment, m is assumed to be 3 for simplicity of
explanation.
[0029] Waveforms representing the process for recovering signals from the number m of scans
are shown in Fig. 7. In Fig. 7, (A) designates the timing of driving the rotary drum
at the speed of R
1/n that is 1/n times the speed for recording. In this case, signals a
0, b
0, a
1, b
1, a
2, b
2, a
3, b
3 are assumed to be reproduced in that order. Character T designates the rotational
period. Character (B) designates the timing of rotation at the speed of
(m = 3) according to the present embodiment, and (C) an envelope of the signal reproduced
by the magnetic heads 51a, 51b. In this way, three scans are effected per track. Also,
as described above, the width W of the magnetic heads 51a, 51b is set to 1.5 times
the track pitch P. Even when the scanning angle deviates from the recording track
angle, therefore, the on-track condition is secured for the most part. The signal
with the highest reproduction output level is retrieved, thereby producing the original
data (waveform D). This data is restored to three times on time base to reproduce
an intended low-speed signal (waveform E).
[0030] As seen from above, at the time of reproduction, the rotary drum 50 is driven at
the speed m/n times higher than for recording, and the magnetic tape 60 is made to
travel at the speed 1/n times higher than for recording. The time-base restoration
n times larger is thus made possible.
[0031] Further, if the value m is set appropriately, a high reproduction frequency can be
obtained and the desired reproduction output level can be secured regardless of the
coefficient n of time-base restoration. Furthermore, the number m of scans per track
permits data reproduction even under the off-track condition, thus eliminating the
need of accurate tracking control.
[0032] Fig. 8 is a block diagram showing an example configuration of a reproducing decoder
70 for processing the whole reproduction system including the process for retrieving
the signal from the number m of scans described above. Numeral 71 designates a memory,
numeral 72 a block detector, numeral 73 an error correction circuit, and numeral 74
a reproducing signal generator. In Fig. 8, the signal reproduced by the magnetic heads
51a, 51b is first applied to the block detector 72. The block detector 72 detects
the sync signal and the ID signal, and stores them at a predetermined position on
the memory 71 based on the track number and the block number in the ID signal. The
error correction circuit 73 corrects the error in the reproduced data using the parity
stored in the memory 71, while at the same time generating a pointer representing
the error condition and storing it in the memory 71. In the process, the memory 71
is supplied with the data on the same track number and the block number a number m
of times. The data with the best error state is finally stored by the pointer. The
reproducing signal generator 74 reads the error-corrected data from the memory 71
in the order of the track numbers and the block numbers and produces the low-speed
data restored on time base.
[0033] The low-speed data signal thus processed in the reproducing decoder 70 is applied
to the receiving system 200 and decoded by the receiving decoder 80 at the transmission
system. The signal thus decoded into the original digital information signal is outputted
from the output terminal 9.
[0034] As described above, the receiving decoder 80 is acceptable as a low-speed processing
device by being arranged in the last stage of the recording-reproducing system 300.
[0035] A block diagram representing a digital information recording-reproducing apparatus
according to another embodiment of the invention is shown in Fig. 9. This embodiment
is an example of a system in which the video software is encrypted and transmitted
as data recordable and reproducible only by the subscriber. In Fig. 9, numeral 15
designates an encryptor, numerals 52a, 52b magnetic heads, numeral 75 a decryptor,
numerals 101, 102, 103 input terminals, numerals 111, 112 A/D converters, numerals
121, 122 bit reduction circuits, numerals 201, 202 bit restoration circuits, numerals
211, 212 D/A converters, and numerals 221, 222, 223 output terminals. Those component
parts corresponding to those in Fig. 1 are designated by the same reference numerals
respectively and will not be described below. In the magnetic heads 52a, 52b, (+)
designates a positive azimuth, and (-) a negative azimuth.
[0036] In the transmission system 100, the video signal applied from the input terminal
101 is A/D converted by the A/D converter 111, and bit-compressed to an appropriate
rate by the bit reduction circuit 122. The audio signal applied from the input terminal
102, on the other hand, is A/D converted by the A/D converter 112 and bit-compressed
to an appropriate rate by the bit reduction circuit 122. These video and audio signals
A/D-converted and bit-compressed, together with the auxiliary data applied from the
input terminal 103, are encrypted and time-division multiplexed by the encryptor 15
and encoded by the transmitting encoder 10. The encrypted signal, as in the embodiment
shown in Fig. 1, is compressed on time base to 1/n by the time-base reduction circuit
20, modulated by the modulator 25, and sent out to the transmission channel 30.
[0037] The receiving system 200, like in the embodiment shown in Fig. 1, demodulates the
signal received through the transmission channel 30 by the demodulator 35, and applies
the demodulated data to the recording encoder 40 of the recording-reproducing system
300.
[0038] The recording-reproducing system 300 encodes the demodulated data through the recording
encoder 40, which data is supplied through the change-over switch 45 to two sets of
magnetic heads 51a, 51b and 52a, 52b, and recorded in the magnetic tape 60 by 2-channel
azimuth. The 2-channel recording using the two sets of magnetic heads 51a, 51b, 52a,
52b can reduce the recording frequency to one half. The rotational speed of the rotating
drum 50 and the travel speed of the magnetic tape 60 are set, for example, at R
2 and V
2 respectively.
[0039] At the time of reproduction, the rotary drum 50 is rotated at the same rate R
2 as for recording (i.e.,
). The magnetic tape 60 is run at the rate of V
2/n that is 1/n the rate for recording, and the signal thus recorded is reproduced
by a set of magnetic heads 51a, 51b. According to this embodiment, the coefficient
n for time-base reduction is set sufficiently large (the larger the value n, the better).
In view of the fact that a number n/2 of tracings per track is possible even for 1-channel
reproduction by the magnetic heads 51a, 51b, sufficient data reproduction is possible
by the same processing through the reproducing decoder 70 as in the embodiment of
Fig. 1. As a result, a single channel of reproducing circuit serves the purpose, thereby
reducing the circuit size. Also, since the rotary drum 50 is driven at the same speed
as at the time of recording, the rotation control is simplified.
[0040] The receiving system 200 receives the signal decoded by the reproducing decoder 70,
decodes through the receiving decoder 80 the signal encoded at the transmission system,
decrypts through the decryptor 75 the signal encrypted at the transmission system,
and thus separates the video signal, the audio signal and auxiliary data. The video
signal and the audio signal thus separated are expanded into the original bit rate
by the bit restoration circuits 201, 202, D/A converted by the D/A converters 211,
212, and outputted from the output terminals 221, 222. Also, the auxiliary data thus
separated are outputted from the output terminal 223.
[0041] In this way, the video signal and the audio signal thus recorded are protected by
arranging the decryptor 75 in the last stage of the recording-reproducing system 300.
Table 1
Video rate (after bit reduction) |
2.5 Mbps |
Audio rate (after bit reduction) |
256 kbps (2 ch) |
Auxiliary data rate |
256 kbps |
Total bit rate (after encoding) |
4 Mbps |
Time-base compression rate |
1/6 (n = 6) |
Transmission rate after time-base reduction |
24 Mbps |
Modulation method |
32 QAM |
Transmission channel |
Cable (bandwidth 6 MHz) |
[0042] Table 1 shows a specific example of the transmission specification of the transmission
system 100 according to the embodiment shown in Fig. 9. Assuming that the post-compression
video bit rate is 2.5 Mbps, the post-compression audio bit rate is 256 kbps, and the
auxiliary data bit rate is 256 kbps, for example, the total bit rate after transmission
encoding is about 4 Mbps. With this bit rate compressed on time base to 1/6 (n = 6),
the transmission rate is 24 Mbps. Assuming also that the CATV cable is a transmission
channel, the bandwidth per TV channel is 6 MHz. If a signal of 24 Mbps in transmission
rate is to be transmitted within the bandwidth of 6 MHz, the optimum modulation system
is 32 QAM (Quadrature Amplitude Modulation).
[0043] Instead of the CATV cable used for the transmission channel in Table 1 above, a communication
satellite may be used for a QPSK (Quadrature Phase Shift Keying) modulation system.
In such a case, the bandwidth of the communication satellite is about 30 MHz per channel
of the transponder, and therefore the transmission rate of about 48 Mbps is available.
As a result, with the same bit rate as in Table 1, two sustaining program software
can be transmitted simultaneously by time-division multiplexing. Alternatively, the
bit rate may be increased twice (with the bit rates of the reduced image and voice
as 5 Mbps and 512 kbps respectively and the bit rate for auxiliary data as 512 kbps)
to improve the video and audio quality. Conversely, the transmission time may be shortened
by time-base reduction to 1/12 (n = 12).
Table 2
|
Example 1 |
Example 2 |
Input bit rate |
24 Mbps |
24 Mbps |
Recording bit rate (after coding) |
36 Mbps |
36 Mbps |
Number of recording channels |
2 |
2 |
Tape width |
1/2 in. |
8 mm |
Tape material |
Metal-oxide |
Metal-evaporated |
Drum diameter |
62 mm |
40 mm |
Drum rotation speed (recording) |
1800 rpm |
1800 rpm |
Tape speed (recording) |
66.7 mm/s |
28.69 mm/s |
Track pitch |
58 µm |
20.5 µm |
Drum rotation speed reproduction) |
1800 rpm |
1800 rpm |
Tape speed (reproduction) |
11.12 mm/s |
4.78 mm/s |
[0044] Table 2 shows specific examples of the specifications of the recording-reproducing
system 300 corresponding to the transmission specifications shown in Table 1 according
to the embodiment of Fig. 9. Example 1 represents the case using an metal-oxide tape
1/2 in. wide, and Example 2 the case using a metal-evaporated tape 8 mm wide. The
input bit rate is 24 Mbps in transmission rate as shown in Table 1, and the recording
bit rate after the encoding in the recording system is about 36 Mbps. With two-channel
recording, the recording rate is 18 Mbps per channel. In Example 1, the drum diameter
is assumed to be 62 mm, and the recording drum rotation speed and the tape speed 1800
rpm and 66.7 mm/s respectively. The related track pitch is 58 µm, and the recording
wavelength is about 0.64 µm. The use of a high-performance metal-oxide tape, therefore,
can achieve a sufficient reproducing signal level. In Example 2, on the other hand,
the drum diameter is assumed to be 40 mm, the recording drum rotation speed and the
tape speed to be 1800 rpm and 28.69 mm/s, respectively. Then the track pitch is 20.5
µm. Under this condition, the recording wavelength is as short as about 0.42 µm, but
a sufficient reproducing signal level can be secured by using the metal-evaporated
tape. In both Examples 1 and 2, the reproducing drum rotation speed is the same 1800
rpm as for recording, while the tape speed is of course set to 11.12 mm/s and 4.78
mm/s respectively, which are 1/6 the corresponding figures for recording.
[0045] Fig. 10 is a block diagram showing an example configuration of the recording encoder
40. 41 designates a memory. 42 an interface circuit, 43 a parity generator circuit,
and 301 a control code generator circuit. In the same diagram, the data demodulated
at the demodulator 35 of the receiving system 200 is first stored in the memory 41
through the interface circuit 42. Fig. 3(A) shows the data thus demodulated. The parity
generator circuit 43 generates a parity based on the demodulated data stored in the
memory 41 and is stored in the memory 41. The recording signal generator circuit 44
reads out the parity and the demodulated data stored in the memory 41, adds thereto
an ID signal and a sync signal including the control code generated at the control
code generator circuit 301, and produces as a signal having a block form as shown
in Fig. 3(B). Fig. 4 shows a configuration example of the ID signal, which is comprised
of, for example, a track number for identifying the recording track, a block number
for identifying the in-track position, control code and the parity for detecting and
correcting an error in the ID signal.
[0046] A configuration of the control signal is shown in Fig. 11. The "program" number is
information indicating the order of a program in the tape, and the "time code" indicates
the lapse of time in the program and tape. The "type" is information indicating whether
the digital information signal recorded is sold or rented. This information may be
subdivided in accordance with whether the information is sold only to a specific user
or the number of days rented. The "recording date" is the date and time recorded,
and the "user No." a user registration number recorded, which are both stored in the
receiving system 200 or the recording-reproducing system 300.
[0047] The control code can be recorded by being distributed in a plurality of blocks to
reduce the redundancy. Also, as shown in Fig. 12, the control code may be recorded
in a region different from the digital information signal. In such a case, the blocks
are configured the same way as the digital information signal recording region, and
the control code is recorded in the part where the demodulated data of Fig. 3(B) is
recorded. The control code may be written severalfold for an improved reliability.
[0048] In the case where the user desiring the service of sale or rent of digital information
signal proposes to the transmitting end, the transmitting end sends to the receiving
end the digital information signal together with the user number and the additional
information indicating the sale or rental. The receiving end discriminates the user
number in the additional information at the recording-reproducing system 300, and
when they are coincident, records the information. In the process, the sale or rental
is discriminated by the additional information and recorded as type information in
the control code.
[0049] According to a further embodiment of the invention, at the time of reproduction,
the rotating drum 50 is driven at the same rate R
1 as at the time of recording, the magnetic tape 60 is fed at the rate of V
1/n that is 1/n times the rate for recording, and the signal thus recorded is reproduced
by the magnetic heads 51a, 51b.
[0050] Fig. 13 is a diagram showing a reproducing track pattern, in which the solid line
represents a recorded track pattern and the dashed line the scanning traces of the
magnetic heads 51a, 51b. In view of the fact that the rotating drum 50 is driven at
the same rate R
1 as at the time of recording and the magnetic tape 60 is fed at the rate of V
1/n that is 1/n times the rate for recording, the scanning pitch of the magnetic heads
51a, 51b is 1/n times the track pitch P. As a result, although the scanning angle
is deviated to some degree, substantially a number n of scans are effected per track.
According to the embodiment under consideration, n is assumed to be 3 for simplicity.
Character W designates the width of the magnetic heads 51a, 51b. Normally, the head
width W is set at, say, 1.5 times larger than the track pitch P.
[0051] Fig. 14 shows waveforms representing the process of retrieving the signal from the
number n of scans. In Fig. 14, (A) designates the timing with the rotary drum 50 driven
at the conventional speed of R
1/n. In this case, signals a
0, b
0, a
1, b
1, a
2, b
2, a
3, b
3 are reproduced in that order. Character T designates the rotational period. Character
(B) designates the timing of rotation made at the rate of R
1 (n = 3) according to this embodiment. Character (C) designates an envelope of the
signal reproduced by the magnetic heads 51a, 51b. As described above, three scans
are made per track and also the width W of the magnetic heads 51a, 51b is set to 1.5
times larger than the track pitch P. Even when the scanning angle deviates from the
recording track angle, therefore, the on-track condition is secured for a considerable
part. As a result, the original data (waveform D) can be produced by retrieving the
signal with the highest reproduction output level. By expanding this signal to three
times on time base, the intended low-speed signal (waveform E) can be reproduced.
[0052] As seen from the above explanation, the reproducing frequency can be increased without
reducing the coefficient n of the time-base reduction by driving the rotating drum
50 for reproduction at the same rate as for recording, thereby securing the desired
reproduction output level. Also, the control of the rotary drum 50 is simplified.
Further, because of the number n of scans per track, the data can be reproduced even
under off-track conditions, thereby eliminating the need of accurate tracking control.
[0053] A block diagram of an example configuration of the reproducing decoder 70 for processing
the whole reproducing system is shown in Fig. 15. Numeral 71 designates a memory,
numeral 72 a block detector, numeral 73 an error correction circuit, numeral 74 a
reproducing signal generator, and numeral 302 a control signal detector. In Fig. 15,
the signal reproduced by magnetic heads 51a, 51b is first applied to the block detector
72. In the block detector 72, a sync signal and an ID signal are detected and stored
in a predetermined position on the memory 71 in accordance with the track number and
the block number in the ID signal. The error correction circuit 73 corrects an error,
if any, in the reproduced data using the parity stored in the memory 71, while at
the same time generating a pointer indicating the error condition and storing the
pointer in the memory 71. In the process, although the same data on the track number
and the block number are stored a number n of times in the memory 71, the data in
the best error condition is finally stored by the pointer. In the reproducing signal
generator 74, the error-corrected data stored in the memory 71 is read out in the
order of the track number and the block number thereby to produce low-speed data expanded
on time base.
[0054] The low-speed data thus decoded for the reproducing system is sent to the receiving
system 200 thereby to resolve the coding made at the transmitting system. The signal
thus decoded to the original digital information signal is produced from the output
terminal 9.
[0055] In this way, the receiving decoder 80 is arranged not before but after the recording-reproducing
system 300, so that the receiving decoder 80 permits low-speed processing.
[0056] The control signal detector 302 identifies the control code and decides whether the
reproduction is to be carried out. In the case of sold information, for example, when
the user number is coincident, the information can be reproduced only by the apparatus
that was used for recording but not by any other apparatuses. With information on
rental, by contrast, the recording data and the rental period are compared, and if
the rental period has passed, the information is prevented from being reproduced.
This control operation can be alternatively performed by the receiving system 200,
in which case the control signal that has been reproduced at the recording-reproducing
system 300 is applied to the receiving system 200.
[0057] Fig. 16 shows a configuration of the control signal according to the embodiment of
Fig. 9. The encrypt information is the one required for decryption. Normally, this
information is stored in the receiving system 200. This encrypt information is stored
as control code, and the encrypt information reproduced at the time of reproduction
is applied to the receiving system 200 to perform decryption. Even when the encryption
is changed, the recorded information can thus be reproduced.
[0058] Also, in the case of rented information, the encryption is regularly changed so that
no encrypt information is recorded in the control code. In this way, the information
that has passed a predetermined length of time cannot be decrypted, thereby making
it possible to manage the rental period.
[0059] In this configuration, it takes some time length before the user wanting to view
a video software requests and receives an actual video data signal. This is because
the transmitter is required to prepare the video data to be transmitted or to stand
by until a transmission channel becomes available. This leads to the problem of when
the user can decide to start the recording-reproducing system 300. The recording-reproducing
system 300, therefore, is desirably controlled by the video data transmitter.
[0060] The embodiment shown in Fig. 17 represents an example of transmitting a recording-reproducing
control signal multiplexed on the digital information signal transmitted by satellite
or cable as a transmission channel. For example, a signal for setting the recording-reproducing
system 300 to a recording (REC) stand-by mode (with the drum 50 rotated while the
magnetic tape 60 kept stationary) is supplied from the recording-reproducing control
signal input terminal 2 approximately two minutes before transmitting a video signal
actually to be recorded, and through the modulator 25 and the transmission channel
30, is transmitted together with the ID code for identifying the receiving home and
the recording-reproducing system 300. The demodulator 35 that has received this signal
sends out the received data to the recording-reproducing control signal detector 65,
and sets the change-over switch 45 of the recording-reproducing system 300 to the
REC stand-by state.
[0061] Next, a signal for setting the recording-reproducing system 300 to REC state is sent
out about one second before transmission of the digital information signal, and the
recording-reproducing control signal detector 65 sets the recording-reproducing system
300 in REC mode. The digital information signal is thus recorded in the magnetic tape
60. Also, at the termination of the digital information signal, a stop signal is immediately
transmitted thereby to stop the recording-reproducing system 300.
[0062] If the user confirms that the magnetic tape 60 has been inserted into the recording-reproducing
system 300 in this configuration, then the remaining operation is performed by the
recording-reproducing system 300 under the control of the transmission system 100.
The recording operation can therefore be performed positively without any special
manipulation. This control data is in one of the three modes including (1) REC stand-by,
(2) REC and (3) stop, and therefore is constituted by two bits at most. Further, the
transmitting time is not limited to the above-mentioned value.
[0063] Fig. 18 shows a transmission data format according to an embodiment of the invention.
In Fig. 18, a block is comprised of a sync signal, an ID data, a parity associated
with the ID data, a digital information signal to be recorded and an error correction
code for the digital information signal. This block is commonly used and similar to
the one used for PCM voice for BS or DAT (Digital Audio Tape).
[0064] As seen from Fig. 18, the recording-reproducing control signal described above, together
with the home and recording-reproducing (VTR) ID signal (user code), is applied to
the ID data section. In the process, the recording-reproducing control signal might
be recorded if the recording format shown in Fig. 3 is employed. It is however possible
to prevent only the control signal from being recorded by the recording signal generator
44. Even if the control signal has been recorded, the reproducing decoder 70 can be
controlled in such a manner as to ignore the particular signal at the time of reproduction.
[0065] Fig. 19 is a block diagram showing another embodiment of the invention. In Fig. 19,
the same component parts as those in Fig. 17 are designated by the same reference
numerals respectively. Numeral 26 designates a modulator, numeral 31 a transmission
channel, and numeral 36 a demodulator. This embodiment is different from that of Fig.
17 in that the recording-reproducing control signal is transmitted through a telephone
line represented by the transmission channel 31, for example, and comprises a dedicated
modulator 26 and a dedicated demodulator 36. The actual transmission data, as described
with reference to the embodiment shown in Fig. 17, has two-bit information. In the
embodiment shown in Fig. 19, no extraneous signal is superimposed on the transmission
channel 30 for transmitting the digital information signal, and therefore the hardware
of the transmitting system is simplified. Also, the modulator 26 and the demodulator
36 can be of low-speed type.
[0066] In the case where the telephone line is used as the transmission channel 31 in the
embodiment under consideration, however, the channel connection time of about two
seconds is required. Also, when the channels are very much congested, the recording-reproducing
system 300 may not be instantaneously switched to REC mode. For this reason, the information
predicting the recording time is preferably transmitted at the time of transmitting
a REC stand-by signal about two minutes before the digital information signal as mentioned
above, so that the recording-reproducing system 300 may be set to REC mode just at
the time of starting the transmission of the digital information signal. The timer
built in the recording-reproducing system 300 can of course be synchronized with the
transmitting timer all the time or at the time of sending out the REC stand-by signal.
This configuration increases the amount of information controlled for the recording-reproducing
system 300 transmitted through the transmission channel 31. The recording-reproducing
system 300, however, can thus be positively controlled to REC stand-by, REC or stop
state by the transmitting end. This method can of course be applied also to the embodiment
shown in Fig. 17.
[0067] The use of the telephone line as the transmission channel 31 permits the bidirectional
reception according to the embodiment shown in Fig. 19. The operating conditions of
the recording-reproducing system 300 can thus be decided at the transmitting end.
Once a modulator and a demodulator are provided at the receiving and transmitting
ends respectively, therefore, an alarm can be issued to the user any time the recording-reproducing
system 300 in malfunction. As a result, the recording operation can be performed more
accurately than according to the embodiment shown in Fig. 1.
[0068] As far as the recording-reproducing system 300 shown in Figs. 1 and 19 is controlled
appropriately, the recording-reproducing system 300 proper may comprise only a change-over
switch operated by the user for switching three modes of reproduce, fast forward feed
and rewind. The apparatus can thus be operated in very simple manner.
[0069] Fig. 20 is a diagram showing an example of the recording format for the magnetic
tape 60 used with the recording-reproducing system 300. In Fig. 20, the magnetic tape
60 is divided into three areas along the longitudinal direction, for example, thereby
to permit continuous recording of three types of video software.
[0070] Assuming that another set of magnetic heads 51a, 51b is added to provide two channels
with n of 6, the recording of two-hour (120-minute) software requires the consumption
amount of the magnetic tape 60 equivalent to 40 minutes for the conventional VTR.
Generally, each movie software is less than two and half hours, and therefore a 50-minute
recording area is required for each such software. If the 160-minute tape sold on
the market is used, on the other hand, three pieces of software can be continuously
recorded.
[0071] In the embodiment shown in Fig. 20, the magnetic tape 60 is preformatted and the
intended information is recorded at the heads of the three recording areas 1, 2 and
3 into which the magnetic tape 60 is divided. These information include the area number,
the recording time, the recording date, and if required, the title. Further, the heads
of the areas 2 and 3 have recorded therein the recording time and date of the digital
information signal respectively for the preceding area respectively.
[0072] Explanation will be made about the case in which three types of software are recorded
at different dates and times. Normally, the digital information signal is recorded
in the areas 1, 2 and 3 in that order. Upon completion of recording up to the area
3, the magnetic tape 60 is rewound and then the area 1 is recorded. At the same time,
the recording date in the head and tail portions of the area 1 is read. In the case
where the digital information signal in the area 1 is still in the valid period, the
magnetic tape 60 is fed fast forward. The recording date in the area 2 is then referenced,
and if it is within the valid period, the record mode is provisionally cancelled and
an input from the user is awaited. Even when the valid period for the software recorded
still remains unexpired, if the particular software is unrequired, the user sets the
recording-reproducing system 300 to REC mode thereby to record in the area 1 or 2.
If the entire software is still needed, on the other hand, the magnetic tape 60 is
changed. This operation is performed in REC stand-by mode.
[0073] The area-divided configuration of the tape allows uniform access to the three areas.
The resulting effect is to disperse tape damage and lengthen the service life of the
magnetic tape 60. Thus the user is not required to unload the magnetic tape 60 frequently
from the recording-reproducing system 300 paying attention to the residual volume
of the magnetic tape 60, thereby improving the mechanical reliability. Also, since
the record-start position is known in advance, the search is effected at very high
speed. Further, the recording-reproducing system 300 can be controlled in simple manner
for a lower hardware cost.
[0074] In the above-mentioned configuration, two areas are used for a digital information
signal exceeding two and half hours in recording time. As shown in Fig. 20, the record
information can be accommodated not in the tail portion of the area 3 but may be in
the portion immediately following the digital information recording section. In similar
fashion, the record information for the areas 1 and 2 may be accommodated in the portion
immediately following the digital information signal recording section of each area.
[0075] These recording time and recording date signals may be accommodated in the ID section
indicated in Fig. 4. Generally, however, the magnetic tape 60 is often in stationary
state at the end of viewing a software. The use of the format described in Fig. 20,
therefore, quickens the search speed. Also, in the case where the user stops the magnetic
tape 60 in the middle of an area, the magnetic tape 60 is fed fast forward or rewound
to the record information section of the particular area.
[0076] Fig. 21 shows a magnetic tape format according to another embodiment. In this embodiment,
the recording information is recorded in accordance with the format of Fig. 21 at
the head of an area immediately before start of recording and at the head of the next
area immediately after the end of recording. The feature of this format is that since
the recording information for a different area is accommodated at the start of the
areas 2 and 3, the search speed is further increased as compared with the embodiment
shown in Fig. 20.
[0077] The area-divided system for the recording magnetic tape 60 is described above. In
the recording-reproducing system 300 shown in Figs. 1 and 19, however, the digital
information signal may be recorded sequentially from the head of the magnetic tape
60 without dividing it into areas.
[0078] The area-recorded information is preferably recorded for about ten seconds and written
in multiplex in consideration of a high-speed search.
[0079] In the system described above, the next REC stand-by signal may be inputted during
reproduction of the digital information signal recorded by the recording-reproducing
system 300. In such a case, the magnetic tape 60 is immediately fed fast forward or
rewound to the next area to ready for recording. At the same time, provision is made
to indicate the REC stand-by mode on the TV screen or in a part of the receiver. Then,
in the case where the recording-reproducing system 300 enters the REC mode, the screen
is switched to normal TV broadcast to indicate REC or turned off. This control operation
can be easily performed normally by the microcomputer mounted on the VTR.
[0080] A normal video signal processing circuit can of course be connected to the recording-reproducing
system 300 to permit the recording of the TV broadcast as in the prior art.
[0081] It will thus be understood from the foregoing description that according to the present
invention, there is realized a digital information recording-reproducing apparatus
for transmitting the software information like audio or video through radio wave or
cable and recording/reproducing them, comprising the function of reducing the recording
time to 1/n and expanding it to the original length on time base at the time of reproduction.
At the same time, the reliability of the reproduced data is improved and the decoder
circuit and the tracking control circuit are simplified. Further, the software information
recorded is protected.
[0082] As described above, according to the invention, there is provided a system for selling
or renting the software like audio or video through radio wave or cable, wherein the
information on customers, rental period, etc. can be easily managed.
[0083] Also, as explained above, by using the magnetic recording-reproducing apparatus according
to the invention, the digital information signal transmitted through a satellite or
cable can be recorded accurately.
[0084] Further, according to another embodiment, the magnetic tape is divided into areas
for recording, thus permitting high-speed search and lengthening the service life
of the magnetic tape.